This invention relates to radiation-detecting arrays. More specifically, this invention relates to modular detector arrays of the type useful in medical diagnostic apparatus, for example, for detection of ionizing radiation, such as X-ray and gamma radiation.
As is known, the xenon gas detector, with respect to which the preferred embodiment of the present invention will be described, is commonly employed in medical diagnostic apparatus, such as computerized tomography (CT) scanners. Briefly, the xenon X-ray detector is made up of a plurality of spaced electrodes which are supported between pairs of parallel ceramic insulating members which are in turn secured to a metal support structure. The electrodes include bias and signal electrode plates connected to a voltage source and instrumentation for measuring the current induced in the individual electrodes by ions and photoelectrons created when the xenon gas is ionized by X-ray or gamma radiation. Xenon gas detectors suitable for use with a CT scanner are disclosed and claimed in U.S. Pat. Nos. Re. 30,644 and 4,119,853, for example, both of which are assigned to the same assignee as the present invention.
Radiation detectors, in general, and especially detectors used in computerized tomography, must detect X-ray photons efficiently and with a high degree of resolution. To obtain good spatial resolution, it is desirable to have the electrode plates spaced closely and uniformly over the entire length of the detector. It is also important for each detector cell to have identical and stable detecting characteristics. A further complication is that of the likelihood of undesirable spurious signals which may exist in such an apparatus. In such a structure where thin metal electrodes must operate in close proximity with a relatively large electrical potential between them, mechanical vibrations transmitted to the plate may significantly vary the distance between them and thus introduce small spurious current changes, known as microphonics, which in turn may cause errors in the X-ray-intensity measurements. In view of these sensitive structural requirements, the particular fabrication techniques employed have been of utmost importance in obtaining a detector structure with the desired performance characteristics.
A modular detector array suitable for use with computerized tomography apparatus is disclosed and claimed in U.S. Pat. No. 4,272,680, issued on June 9, l981 to D. J. Cotic. This patent is assigned to the same assignee as the present invention and is incorporated herein by reference. The modular array, which will be described in greater detail hereinafter, is composed of a plurality of detector modules supported between a pair of substantially parallel support members. The detector modules are made up of a plurality of parallel plates held between two electrically insulating substrates. The individual modules are secured to the parallel-supporting members by means of threaded fasteners, thereby permitting the modules to be quickly and easily removed and replaced as necessary. Although this detector array has performed satisfactorily, a need has been recognized to provide a modular detector array having the desired performance characteristics and which features improved ease of assembly and enhanced strength of the detector module. Additionally, it has been determined that the detector array should exhibit a construction which reduces the stress imposed on the insulating substrate (typically fabricated from a ceramic material). It is, therefore, an object of the invention to provide a new and improved modular detector array having these and other advantageous features which will be more fully described hereinafter.